The OSM data is vastly superior to Google, but the Port Soderick area could benefit from addition of much more detail.

1) Port Soderick Glen
Would be good just to have a label! Land use should be shown as woodland, and the wildflower meadow shown. Position of river needs fixing (boundary is probably accurate)
There is a small error on one footpath (but otherwise seems to be accurately mapped)

2) Old Castletown Road
Always difficult to give directions to our house. Wouldn't it be great if OSM had house names and building outlines for the area.

3) Arragon
Syd was part of the battle to stop the landowners extinguishing the footpath rights over this private road. It is an absolute tragedy that neither the road, or many of the footpaths are shown.

But where to start?
Conscious that I could damage other peple's data. Need to get in touch with local OSM community (if any active) Good start would be to ask Juan.

Many areas are monitored by local mappers, I monitor my local area. Try making a few additions and you may be contacted by anyone who is interested.

Be bold. Just add detail. If you are adding stuff you have seen on the ground then it is going to be welcome. OSM is a wiki, so people expect their work to be extended and improved. If you really make a mistake, it can be corrected, so don't worry.

If you need help and cannot find out otherwise, just ask someone who "runs" by - e.g. those who comment here.

A tip at your first edit: should get tags what it is. Would chalet fit? You can select it in the editor Potlatch2 on the left side → accomodation or you can use the Advanced mode to type the tag manually? The building outline could be added as separate object. It can be traced from the aerial imagery background supplied in Potlatch2 - the OSM data editor which you used.

Just play a bit with the editor, if you accidentally break something it can be restored. Start slowly, but just try it.